Two fatalities in the first 24 hours of Labour Weekend dashed police hopes that their get-tough stance on speed would keep the roads safe.

Police have clamped down on drivers caught exceeding the speed limit - they will ticket anyone over 4km/h above limits instead of the usual 10km/h threshold.

At Queen's Birthday when they did this, there was one fatality - the lowest toll for any long weekend since 1956 - but on Friday night a man in his 60s died in a crash near Norsewood.

Inspector Hugh Flower said a Ford Falcon towing a tandem car trailer carrying a 4wd vehicle was headed north over a rise on State Highway 2 at Matamau about 8.15pm.

Flower said the trailer became unstable, the driver lost control and the trailer crossed the centre line, colliding with a south-bound Honda car.

The driver of the Honda was killed instantly, and a passenger was taken to hospital with minor injuries.

Dannevirke police constable Dave Power, who attended the scene, said the south-bound car was "pretty much destroyed" in the crash.

The second fatal accident happened when a University of Otago student was killed and two children airlifted to hospital after a head-on smash between two cars on a mountainous stretch of road near Gore yesterday about 12.15pm.

It is understood the woman, in her early twenties, was driving home to Invercargill for the long weekend.

Emergency staff at the scene said it looked like one of the cars had crossed the centre line. The woman's car "bounced and rolled" several times, smashing down a bank.

"The car was pretty wrecked. It wasn't tidy, we had to cut the roof off to extract the deceased woman," a firefighter from Mataura said.

"We're all very sad. There's a family that don't have their daughter any more."

An 11-year-old girl in the other car was flung on to the road, suffering chest injuries and broken ribs. Last night she was in intensive care at Dunedin Hospital with serious but not life-threatening injuries. Her eight-year-old brother was also injured, but managed to wriggle from the back to sit next to his father who was trapped in the driver's seat.

Names of the two dead had not been released.

Eight people died in crashes last Labour Weekend.